Fabrication of multilayer epoxy/bismuth oxide composites for gamma radiation shielding applications

This study presents the fabrication and evaluation of multi-layered epoxy resin composites loaded with bismuth oxide (Bi2O3, 10–30 wt%) as eco-friendly, lightweight alternatives to lead shielding. Composite specimens (2.0 cm total thickness) were synthesized using a room-temperature sequential casting protocol across single-, double-, and triple-layer configurations. Restricting sub-layer casting thickness (0.67–1.0 cm) suppressed gravitational particle sedimentation and exothermic heat accumulation, resulting in homogeneous filler dispersion and strong interfacial covalent bonding. Radiation shielding properties were evaluated under narrow-beam geometry using 57Co (122 keV), 133Ba (356 keV), and 137Cs (662 keV) sources. Attenuation performance correlated positively with Bi2O3 content and sub-layer partitioning while decreasing at higher photon energies due to transitions from photoelectric absorption to Compton scattering. The triple-layer 30 wt% composite (Bi30-3L) demonstrated superior performance under 122 keV gamma irradiation, yielding a linear attenuation coefficient (µ) of 0.738 ± 0.0142 cm−1, half-value layer (HVL) of 0.939 cm, tenth-value layer (TVL) of 3.120 cm, and 77.15 ± 0.92% attenuation efficiency. Notably, the required TVL (3.120 cm) provides an effective, lead-free alternative thickness suitable for desktop shielding applications. Overall, these multi-layered epoxy/Bi2O3 composites represent a promising, non-toxic, and ergonomically superior replacement for primary radiation protection in nuclear medicine procedures involving low-energy radionuclides such as 99mTc (140 keV).